Kei Nishikori vs. John Isner: Score, Reaction from 2015 Citi Open

Kei Nishikori captured the 2015 Citi Open title Sunday following a 4-6, 6-4, 6-4 win over John Isner in Washington, D.C.

For Nishikori, the victory is a small measure of revenge after Isner won 6-4, 6-3 in the quarterfinals of the Miami Open back in April.

In the semifinals of the Citi Open, Nishikori was tasked with facing another relatively big server, Marin Cilic, who wins on average 77 percent of his first-serve points and earns just a shade under 12 aces a match.

Nishikori is one of the better returners on the ATP Tour—seventh in first-service return points won (36 percent)—but he admitted that his strategy against Cilic at times relied on blind luck.

"I tried to hit a little more aggressive," he said after the win, per the Associated Press (via USA Today). "Some of the shots I have to close my eyes and just hit the ball."     

The No. 5 player in the world would need equal parts luck and aggression in order to topple Isner in the final.

It became readily apparent Isner would be doing his opponent no favors. In the first set, he picked up six aces and won 80 percent of his first-serve points. Not only was Isner getting a ton of power behind his serves, but he was also applying incredible kick and working the angles to keep Nishikori guessing.

Erik Gudris of Tennis Now was particularly impressed with how Isner danced out of danger on serve:

Nishikori was just as good on his first serve, albeit relying more on precision over power. He dropped three of his 16 first-service points across the first set.

However, Nishikori's second serve was much less effective and opened the door for Isner to grab a service break. He nearly did so in the fourth game, with his forehand shot going into the net at break point, per TennisTV:

Isner got another opportunity in the 10th game, this time making the most of his chance, per the New York Times' Ben Rothenberg:

Nishikori quickly moved past the disappointment of dropping the first set. He broke Isner's serve in the first game of the second set and took a 2-0 set lead after holding serve.

Problems for Isner arose when he would get into any sort of rally. Nishikori's ground game is far superior, and his backhand is one of the best shots on the ATP Tour. Nishikori, when given the chance, did a great job of working Isner around the court and keeping him away from his forehand.

This stat from Nick Lester demonstrated just how much better Nishikori was in extended rallies:

After the third game of the set, Isner received a medical timeout so a trainer could work on his right shoulder. Whatever the trainer did, it seemed to work, as Isner resumed dominating on serve.

Of course, his issues everywhere else remained as Nishikori was a perfect 14-of-14 on first serve in the second set. Isner couldn't even force a break-point opportunity as Nishikori forced a decisive third set.

As TennisTV noted, Nishikori has earned a reputation as a great closer on the ATP Tour:

The margin for error in the third set was small for both competitors. Each player had to hope he could steal a service break and remain dominant on serve; otherwise, everything would fall apart.

The question was who would blink first.

It proved to be Isner, who dropped serve in the third game of the set to fall behind 1-2. From there, he was fighting an uphill battle. Fatigue was beginning to set in, and he was becoming less and less effective from the baseline.

Nishikori also took the step of putting less power into his serves. That allowed him to better place his serves and put Isner even more on the back foot to start the point. Across the entire set, Nishikori dropped just three points on serve.

This win is a big feather in the cap of Nishikori ahead of the 2015 U.S. Open, which begins in a little over three weeks. The 25-year-old will have a hard time topping last year's runner-up finish, but he looks to be getting back to that level after his disappointing second-round exit at Wimbledon.

For Isner, the defeat is another reminder that he will continue struggling to break through at major tournaments until he can become more consistent from the baseline.

Note: Match and player stats are courtesy of ATPWorldTour.com.